Benchmark calculations of 29Si–1H spin–spin coupling constants across double bond

Benchmark calculations of geminal and vicinal ²⁹Si–¹H spin–spin coupling constants across double bond in three reference alkenylsilanes have been carried out at both DFT and SOPPA levels in comparison with experiment. At the former, four density functionals, B3LYP, B3PW91, PBE0 and KT3, were tested in combination with five representative basis sets. At the latter, three main SOPPA‐based methods, SOPPA, SOPPA(CC2) and SOPPA(CCSD), were examined in combination with the same series of basis sets. On the whole, the wavefunction methods showed much better results as compared to DFT, with the most efficient combination of SOPPA/cc‐pVTZ‐su2 characterized by a mean absolute error of only 0.4 Hz calculated for a set of nine coupling constants in three compounds with a sample span of around 40 Hz. Copyright © 2012 John Wiley & Sons, Ltd.     

Synthesis and Biological Activity of 4-Aryl-3,6-dihydroxy-6-methyl-4,5,6,7-tetrahydro-2H-indazole-5-carboxamides

Russian Journal of General Chemistry - The reaction of 2-aryl-4-hydroxy-4-methyl-6-oxocyclohexane-1,3-dicarboxamides with hydrazine hydrate in ethanol gave...     

Synthesis and properties of quinazoline derivatives containing cymantrenyl group

The synthesis of new quinazoline derivatives with 2,3- and 4-positioned cymantrenyl fragment is described. Alkylation of 2-substituted quinazolin-4-ones with cymantrenylalkyl bromides on using K₂CO₃, potassium tert-butoxide, and sodium hydride as bases has been studied. It is established for the first time that condensation of 2-methylquinazolin-4-ones with aldehydes can cause elimination of the substituent at the nitrogen atom in position 3. The new cymantrene derivatives possess fluorescence properties.     

3,4,5,6-Tetrafluoro-1,2-dehydrobenzene in reactions with 1,2,4-triazines

Tetrafluoro-substituted aryne, 3,4,5,6-tetrafluoro-1,2-dehydrobenzene, has been generated in situ from 2-amino-3,4,5,6-tetrafluorobenzoic acid, and its reactivity in reactions with 1,2,4-triazines as dienes has been studied. In these reactions, the corresponding azine ring transformation products, i.e., 1,2,3,4-tetrafluoro-10-(1H-1,2,3-triazol-1-yl)pyrido[1,2-a]indoles, have been obtained, in the case of triazines activated by the presence of electron-withdrawing groups, such as 6-aryl-3-(2-pyridyl)-5-cyano-1,2,4-triazines. The crystal structure of the obtained products was confirmed by X-ray diffraction analysis.     

Curing of Oligomers with Thermoreactive Norbornene,Chalcone, and Maleimide Groups

Curing of powdered chalcone-containing oligoimides with terminal maleimide or norbornenedicarboxylic acid imide groups was studied by differential scanning calorimetry. The calorimetric characteristics of curing were discussed in relation to the chemical structure and conformational isomerism of the oligomers.     

Stabilization of [2.2]paracyclophane anion as a result of transannular interaction

The review surveys methods for the construction of bi- and polycyclic nitrogen-, oxygen-, and sulfur-containing heterocycles based on reactions of 2-halobenzoyl chlorides with dinucleophiles.     

Fluorinated azines and benzazines containing oxygen or sulfur atoms

In the frames of this review article the recently obtained data on synthetic approaches to fluorinated oxa(thia)azines and benzazines, their chemical properties, structure, and biological activity have been analyzed.     

Fluorine-containing quinazolines annulated at the pyrimidine ring

Fluorine-containing quinazolines annulated at the sides [a] and [c] were synthesized by the reaction of 2- and 4-hydrazino-substituted quinazolines with aldehydes and subsequent oxidative cyclization. Annulation at the side [b] was performed by alkylation of 2-alkylthio-4(3H)-quinazolinones with bromoethanol and ipso-substitution of the alkylthio group.

     

Chromium,vanadium, molybdenum,tungsten, magnesium,and aluminum hydrotalcite hydroxo salts and oxide catalysts on their base

A method is developed for the synthesis of chromium-containing catalysts for the oxidative dehydrogenation (ODH) of alkanes, comprising the precipitation, from nitrate solutions, of mixtures of isomorphic hydrotalcite-type magnesium aluminum and magnesium chromium hydroxocarbonates and the incorporation of oxovanadate, oxomolybdate, and oxotungstate ions by means of anion exchange and subsequent heat treatment. A series of oxide catalyst samples with progressively more complex compositions were prepared: Mg-Al, V-Mg-Al, V-Mo-Mg-Al, Cr-V-Mg-Al, Cr-V-Mo-Mg-Al, and Cr-V-Mo-W-Mg-Al. The catalytic properties of these complex oxides in the ODH of ethane and propane are improved with progressively complex compositions. Chromium-containing catalysts have higher selectivities and provide higher conversions compared to state-of-the-art iron- and nickel-containing oxides.     

Structure of complexes formed by dissolution of palladium diacetate in methanol and chloroform. In situ NMR study

The behavior of palladium diacetate cyclic trimer [Pd(OAc)(2)](3) (1) upon its dissolution in methanol and wet chloroform was studied by (1)H and (13)C NMR including 2D-HSQC and 2D-DOSY techniques. Upon dissolution, trimer 1 reacts with methanol and is completely transformed first into the methoxo complex Pd(3)(μ-OMe)(OAc)(5) (2), which already at -18 °C undergoes a slow exchange of second bridging acetate ligand between the same palladium atoms to form the symmetric dimethoxo complex Pd(3)(μ-OMe)(2)(OAc)(4), the maximum relative concentration of which reaches 20-30 mol % of initial loading trimer 1. Along with the dimethoxo complex, both soluble and insoluble polynuclear palladium clusters are gradually formed at -18 °C, and their total amount reaches up to 60% of the starting Pd(2+) loading. The increase of temperature to 27 °C results in the reduction of palladium(II) to Pd metal by methanol, which is oxidized and transformed into formaldehyde hemiacetal and methyl formate. Upon dissolution in wet chloroform, trimer 1 is reversibly hydrolyzed to the hydroxo complex Pd(3)(μ-OH)(OAc)(5) (10) in ratio 1/10 ≈ 3/1. The temperature decrease and addition of acetic acid shift the equilibrium in this system toward trimer 1, and addition of water shifts it in the opposite direction. Addition of methanol to the equilibrium mixture of 1 and 10 results in the fast exchange of bridging acetate in trimer 1 by the μ-OMe group. Substitution of the μ-OH ligand by μ-OMe in 10 occurs in parallel but more slowly. Complex 2 formed in both cases is more stable in chloroform than in methanol.